U.S. patent application number 11/892361 was filed with the patent office on 2009-02-26 for energy management system for membrane separation device.
This patent application is currently assigned to Flair Corporation, a Delaware Corporation. Invention is credited to John E. Thelen.
Application Number | 20090049983 11/892361 |
Document ID | / |
Family ID | 40378522 |
Filed Date | 2009-02-26 |
United States Patent
Application |
20090049983 |
Kind Code |
A1 |
Thelen; John E. |
February 26, 2009 |
Energy management system for membrane separation device
Abstract
An energy management system for a membrane separation device,
including: a membrane having permeate and non-permeate portions; a
membrane housing which encases said membrane; a feed fluid inlet
conduit; a purge inlet conduit; a non-permeate product fluid outlet
conduit; and, a purge outlet conduit, configured to carry purge
fluid out of the membrane dryer; at least one purge inlet flow
control valve connected to said purge inlet conduit, a sensor
configured to measure the contaminant level of fluids exiting the
purge outlet conduit; and, a controller receiving an output signal
from the sensor and transmitting a valve control signal to the at
least one purge inlet flow control valve.
Inventors: |
Thelen; John E.; (Ocala,
FL) |
Correspondence
Address: |
BAKER & HOSTETLER LLP
WASHINGTON SQUARE, SUITE 1100, 1050 CONNECTICUT AVE. N.W.
WASHINGTON
DC
20036-5304
US
|
Assignee: |
Flair Corporation, a Delaware
Corporation
|
Family ID: |
40378522 |
Appl. No.: |
11/892361 |
Filed: |
August 22, 2007 |
Current U.S.
Class: |
95/10 ; 95/12;
96/408 |
Current CPC
Class: |
B01D 2311/246 20130101;
B01D 53/268 20130101; B01D 2313/90 20130101; B01D 2311/16 20130101;
B01D 63/02 20130101; B01D 2313/18 20130101 |
Class at
Publication: |
95/10 ; 95/12;
96/408 |
International
Class: |
B01D 46/44 20060101
B01D046/44; B01D 53/30 20060101 B01D053/30 |
Claims
1. An energy management system, comprising: a membrane separation
device, wherein the membrane separation device comprises: a
membrane having permeate and non-permeate portions; a membrane
housing which encases said membrane; a feed fluid inlet conduit; a
purge inlet conduit; a non-permeate product fluid outlet conduit;
and, a purge outlet conduit, configured to carry a purge fluid out
of the membrane separation device; at least one purge inlet flow
control valve connected to said purge inlet conduit, an exhaust
sensor configured to measure an exhaust permeate fluid
concentration of fluids exiting the purge outlet conduit; and, a
controller receiving an output signal from the exhaust sensor and
transmitting a valve control signal to the at least one purge inlet
flow control valve.
2. The energy management system of claim 1, wherein the exhaust
sensor includes a relative humidity transmitter.
3. The energy management system of claim 1, wherein the membrane
separation device includes an integral purge control feature.
4. The energy management system of claim 1, wherein the membrane
separation device includes hollow fiber membranes.
5. The energy management system of claim 1, wherein the membrane
separation device includes a membrane dryer.
6. The energy management system of claim 1, wherein the at least
one purge inlet flow control valve is configured to provide
continuously modifiable flow rates.
7. The energy management system of claim 1, wherein the at least
one purge inlet flow control valve includes a plurality of on-off
valves each connected to the controller.
8. The energy management system of claim 7, wherein the plurality
of on-off valves includes at least two solenoid valves.
9. The energy management system of claim 7, further comprising an
inlet sensor configured to measure an inlet permeate fluid
concentration of fluids entering the feed fluid inlet conduit.
10. The energy management system of claim 1, further comprising an
inlet sensor configured to measure an inlet permeate fluid
concentration of fluids entering the feed fluid inlet conduit
connected to the controller.
11. The energy management system of claim 1, further comprising an
orifice for metering flow into the purge inlet conduit.
12. The energy management system of claim 1, further comprising a
manifold mounted to the membrane housing.
13. The energy management system of claim 12, wherein the at least
one purge inlet flow control valve is mounted to the manifold.
14. A method of using an energy management system in conjunction
with a membrane separation device, comprising: directing fluid into
the membrane separation device, wherein the membrane separation
device comprises: a membrane having permeate and non-permeate
portions; a membrane housing which encases said membrane; a feed
fluid inlet conduit; a purge inlet conduit; a non-permeate product
fluid outlet conduit; and, a purge outlet conduit, configured to
carry an exhaust fluid out of the membrane separation device;
measuring an outlet permeate fluid concentration of fluids exiting
the purge outlet conduit using an exhaust sensor; transmitting a
first output signal from the exhaust sensor to a controller;
transmitting a valve control signal from the controller to at least
one purge inlet flow control valve; and directing flow into the
purge inlet conduit based on the measured outlet permeate fluid
concentration and using the at least one purge inlet flow control
valve connected between said purge inlet conduit and said
controller.
15. The method of using the energy management system of claim 14,
wherein the exhaust sensor is a relative humidity transmitter.
16. The method of using the energy management system of claim 14,
further comprising: measuring an inlet permeate fluid concentration
of feed fluid entering the feed fluid inlet conduit using an inlet
sensor; transmitting a second output signal from the inlet exhaust
sensor to the controller.
17. The method of using the energy management system of claim 14,
wherein directing flow into the purge inlet conduit using the at
least one purge inlet flow control valve connected between said
purge inlet conduit and said controller further comprises
configuring the at least one purge inlet flow control valve to
provide continuously modifiable flow rates.
18. The method of using the energy management system of claim 14,
wherein transmitting the valve control signal from the controller
to the at least one purge inlet flow control valve includes
transmitting the valve control signal to a plurality of on-off
valves.
19. The method of using the energy management system of claim 14,
further comprising metering flow into the purge inlet conduit using
an orifice.
20. An energy management system, comprising: membrane separation
means for separating a permeate fluid from a non-permeate fluid,
including: membrane housing means for encasing said membrane
separation means; feed inlet means for flowing a feed fluid into
the membrane separation means; purge inlet means for flowing a
purge fluid into the membrane separation means; product outlet
means for flowing a product fluid out of the membrane separation
means; and, purge outlet means for flowing an exhaust fluid out of
the membrane separation means; purge inlet flow control means for
controlling the flow of purge fluid into the purge inlet means,
exhaust sensor means for measuring an exhaust permeate fluid
concentration of exhaust fluid exiting the purge outlet means; and
controller means for receiving an output signal from the exhaust
sensor means and transmitting a valve control signal to the purge
inlet flow control means.
21. The energy management system of claim 20, further comprising an
inlet sensor means, connected to the controller, for measuring an
inlet permeate fluid concentration of the feed fluid entering the
feed inlet means.
22. The energy management system of claim 20, further comprising
orifice means for metering flow into the purge inlet means.
Description
FIELD OF THE INVENTION
[0001] This invention relates generally to an energy management
system for a membrane separation device. More particularly, the
invention relates, for example, to regulating purge flow rate to
reduce excessive purge fluid consumption.
BACKGROUND OF THE INVENTION
[0002] It is known in the art that compressed air, which has
several uses including in food packaging, pharmaceutical labs and
integrated circuit manufacturing, may be treated to remove
contaminants and water vapor. Compressed air is treated before use
in manufacturing systems to remove water vapor and contaminants
from the air that may spoil the end product or at least increase
the cost of production by robbing the system of power and
efficiency. As untreated compressed air is moved through a system,
the temperatures may drop, which in turn may cause the water vapor
to condense. The introduction of water may cause rust or leakage of
the air lines. With conventional compressed air treatment
equipment, system power may be preserved, operating expenses may be
reduced, and production quality may be improved by removing water
vapor from compressed air.
[0003] It is known in the art that cleaning compressed air using a
membrane dryer removes contaminants and water vapor and also,
reduces its dew point, which is the temperature at which the air
must be cooled, at constant barometric pressure, for the water
vapor component to condense into water. Compressed air may be moved
through a bundle of hollow fibers, which may be composed of a
membrane specifically designed to attract water vapor. Thus, as
compressed air passes on one side of the membrane, the water vapor
is absorbed into the membrane, passing quickly through, where it is
desorbed into the purge stream on the opposite side of the
membrane. The dryer is driven by the differential in water vapor
pressure across the membrane. Conventional membrane dryers use a
portion of the dried compressed air as the purge stream. This dried
air is expanded to low pressure to further reduce the water vapor
partial pressure, thus increasing the driving force for the
process. The purge air stream flushes the water vapor from the
permeate side of the hollow fibers and thus, continuously purges
the membrane of water vapor.
[0004] Similarly, separation of other fluid mixtures may be
accomplished by passing the fluid mixture on one side of a
semi-permeable membrane, as long as there is one or more highly
permeable components and other less permeable components. The
membrane may then be purged by sweeping the system using the stream
that has been stripped of the highly-permeable component. The purge
stream would then carry the more permeable components out of the
system.
[0005] In conventional membrane gas separation devices, continuous
sweep or purge may be used to increase the partial pressure
differential that drives the system, improve the product gas purity
and enhance productivity of the membrane. However, the continuous
purge of the membrane can be very expensive. In the case of a
membrane air dryer, continual purging of the membrane dryer with a
constant flow from the dryer outlet wastes resources because
whenever the dryer is used at less than design capacity, lower
purge rates can be used to maintain product purity.
[0006] Many membrane gas separation systems require the use a purge
gas stream to carry off the gas constituents that permeate the
membrane wall. Most conventional membrane separation systems
continuously purge at a constant rate. Attempts have been made to
decrease the amount of gas used to sweep the membrane but these
previous systems control purge by monitoring the outlet gas purity
which can be very costly because instrumentation capable of
monitoring low contaminant levels at the outlet is often expensive.
Because this purge stream comprises the primary operating cost
associated with operating a membrane separation system, there is a
benefit in minimizing the purge flow rate without adding costly
instruments to the system. Accordingly, it is desired to provide a
system that selectively purges the membrane while avoiding excess
purging.
SUMMARY OF THE INVENTION
[0007] The foregoing needs are met, to a great extent, by the
invention, wherein aspects of an energy management feature may be
added to membrane separation system to allow selective purge of the
membrane. The invention enables a gas separation system that
selectively purges the membrane by monitoring the amount of
permeate being carried out with the purge outlet stream. Example
embodiments of the invention provide an energy management system
which regulates the purge flow rate based on the relative humidity
(RH) of the purge outlet stream.
[0008] In accordance with an embodiment of the invention, an energy
management system for a membrane separation device may include a
membrane separation device, having: a membrane having permeate and
non-permeate portions; a membrane housing which encases said
membrane; a feed fluid inlet conduit; a purge inlet conduit; a
non-permeate product fluid outlet conduit; and, a purge outlet
conduit, configured to carry purge fluid out of the membrane
separation device. In some embodiments, the membrane separation
device includes an integral purge control feature. In other
embodiments, the membrane separation device may include hollow
fiber membranes. The membrane separation device may also include a
membrane dryer.
[0009] The energy management system may also include at least one
purge inlet flow control valve connected to said purge inlet
conduit; an exhaust sensor configured to measure an exhaust
permeate fluid concentration of fluids exiting the purge outlet
conduit; and, a controller receiving an output signal from the
exhaust sensor and transmitting a valve control signal to the at
least one purge inlet flow control valve. In some embodiments, the
exhaust sensor may include a relative humidity transmitter
configured to measure the exhaust relative humidity of fluids
exiting the purge outlet conduit. In example embodiments, the at
least one purge inlet flow control valve is configured to provide
continuously modifiable flow rates. In some embodiments, the at
least one purge inlet flow control valve includes a plurality of
on-off valves each connected to the controller, which for example
may include two solenoid valves.
[0010] The energy management system may include an inlet sensor
configured to measure an inlet permeate fluid concentration of
fluids entering the feed fluid inlet conduit. The energy management
system may also include an orifice for metering flow into the purge
inlet conduit and/or a manifold mounted to the membrane housing. In
such an embodiment, at least one purge inlet flow control valve may
be mounted to the manifold.
[0011] In accordance with the invention, a method of using an
energy management system in conjunction with a membrane separation
device, includes: directing fluid into the membrane separation
device, wherein the membrane separation device comprises: a
membrane having permeate and non-permeate portions; a membrane
housing which encases said membrane; a feed fluid inlet conduit; a
purge inlet conduit; a non-permeate product fluid outlet conduit;
and, a purge outlet conduit, configured to carry an exhaust fluid
out of the membrane separation device.
[0012] The method of using an energy management system in
conjunction with a membrane separation device may also include
measuring an outlet permeate fluid concentration of fluids exiting
the purge outlet conduit using an exhaust sensor; transmitting a
first output signal from the exhaust sensor to a controller;
transmitting a valve control signal from the controller to at least
one purge inlet flow control valve; and directing flow into the
purge inlet conduit based on the measured outlet permeate fluid
concentration and using the at least one purge inlet flow control
valve connected between said purge inlet conduit and said
controller.
[0013] The method of using the energy management system may further
include: measuring an inlet permeate fluid concentration of feed
fluid entering the feed fluid inlet conduit using an inlet sensor
and transmitting a second output signal from the inlet exhaust
sensor to the controller. In some embodiments of the invention, the
step of directing flow into the purge inlet conduit using the at
least one purge inlet flow control valve connected between said
purge inlet conduit and said controller may include configuring the
at least one purge inlet flow control valve to provide continuously
modifiable flow rates. In some embodiments, transmitting the valve
control signal from the controller to the at least one purge inlet
flow control valve includes transmitting the valve control signal
to a plurality of on-off valves. The method may also include
metering flow into the purge inlet conduit using an orifice.
[0014] In example embodiments of the invention, an energy
management system may include: membrane separation means for
separating a permeate fluid from a non-permeate fluid, which may
include: membrane housing means for encasing said membrane
separation means; feed inlet means for flowing a feed fluid into
the membrane separation means; purge inlet means for flowing a
purge fluid into the membrane separation means; product outlet
means for flowing a product fluid out of the membrane separation
means; and, purge outlet means for flowing an exhaust fluid out of
the membrane separation means. The energy management system may
also include: purge inlet flow control means for controlling the
flow of purge fluid into the purge inlet means, exhaust sensor
means for measuring an exhaust permeate fluid concentration of
exhaust fluid exiting the purge outlet means; and controller means
for receiving an output signal from the exhaust sensor means and
transmitting a valve control signal to the purge inlet flow control
means. The energy management system may further include an inlet
sensor means, connected to the controller, for measuring an inlet
permeate fluid concentration of the feed fluid entering the feed
inlet means. In some embodiments the energy management system also
includes orifice means for metering flow into the purge inlet
means.
[0015] There has thus been outlined, rather broadly, certain
embodiments of the invention in order that the detailed description
thereof herein may be better understood, and in order that the
contribution to the art may be better appreciated. There are, of
course, additional embodiments of the invention that will be
described below and which will form the subject matter of the claim
appended hereto.
[0016] In this respect, before explaining at least one embodiment
of the invention in detail, it is to be understood that the
invention is not limited in its application to the details of
construction and to the arrangements of the components set forth in
the following description or illustrated in the drawings. The
invention is capable of embodiments in addition to those described
and of being practiced and carried out in various ways. Also, it is
to be understood that the phraseology and terminology employed
herein, as well as the abstract, are for the purpose of description
and should not be regarded as limiting.
[0017] As such, those skilled in the art will appreciate that the
conception upon which this disclosure is based may readily be
utilized as a basis for the designing of other structures, methods
and systems for carrying out the several purposes of the invention.
It is important, therefore, that the claims be regarded as
including such equivalent constructions insofar as they do not
depart from the spirit and scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a schematic showing of an energy management
system, according to an embodiment of the invention.
[0019] FIG. 2 is a schematic showing of an energy management
system, according to another embodiment of the invention.
[0020] FIG. 3 is a schematic showing of an energy management
system, according to yet another embodiment of the invention.
DETAILED DESCRIPTION
[0021] Various embodiments of the invention provide for an energy
management system for use with, for example, a membrane separation
device. In some arrangements, the invention may be utilized as an
energy conservation feature for modulating purge gas consumption of
a compressed air membrane dryer by incorporating a device to
measure the level of contaminants in the purge gas exiting the
membrane. It should be understood, however, that the invention is
not limited in its application to compressed air membrane dryer
systems, but, for example, with other gas separation systems that
utilize a product fluid sweep. Embodiments of the invention will
now be further described with reference to the drawing figures, in
which like reference numbers refer to like parts throughout.
[0022] FIG. 1 is a schematic showing of an energy management system
100, according to an embodiment of the invention. The system 100
may be used in conjunction with a membrane separation device, such
as a membrane dryer 105, as shown in FIG. 1. The membrane dryer 105
may be attached to a purge flow control valve 110 which may be
controlled by a controller 115. The controller 115 may receive an
analog output signal 117 from a sensor, such as an RH Transmitter
120, which measures concentration levels of a certain fluid stream.
In example embodiments of the invention, a valve control signal
125, which may be pneumatic, electrical or other suitable form,
enables communication between the controller 115 and the purge flow
control valve 110.
[0023] In example embodiments of the invention, wet compressed air
W from a compressor may enter the membrane dryer 105 at wet air
inlet I. The compressed air passes through a membrane fiber bundle
130, which is housed within a membrane dryer shell or bowl 135. The
membrane fiber bundle 130, which may be helical or other shapes, is
specifically designed to attract water vapor and in one embodiment
of the invention, may be comprised of a bundle of hollow fibers. As
air passes through the hollow membrane fibers of the membrane fiber
bundle 130, water vapor is absorbed from the stream W.
[0024] In example embodiments of the invention, a differential
partial pressure of water vapor exists between the inside of the
membrane fiber bundle 130 and the outside so that water vapors will
migrate to the outside shell of the fiber bundle 130. Thus, as the
compressed air inlet stream W passes through the inside of the
membrane fibers, the water vapor is absorbed on the membrane
material coating the fibers and passes quickly through the walls of
the fibers to the outer layers of the membrane. In order to operate
continuously, the outer layers of the bundle 130 must be purged of
water vapors, as further discussed below.
[0025] The bulk of the dry air travels through the membrane dryer
105 and exits the system 100 through a dry air outlet D. The
product dry air is then used to perform work or otherwise used in
industrial processing and manufacturing. A smaller portion of the
product dry air is diverted to the purge flow control valve 110. In
example embodiments, such as for use with a proportional solenoid
valve, the control valve may utilize a continuously variable
throttle, for example 1-5 volts or more of direct current (VDC), to
enable continuous changes in flow amounts.
[0026] In example embodiments of the invention, the purge air
stream P may run counter current to the inlet stream W and at lower
pressure, creating a driving force for the drying process. The
purge air that passes through the open valve 110 is swept across
the outside of the membrane fiber bundle 130, creating a moisture
gradient. As such, once the water vapor reaches the outside of the
membrane fiber bundle 130, it is swept off the surface by the purge
air inlet stream P. This low pressure wet purge air, is then
exhausted from the system 100 through purge exhaust stream E.
[0027] In example embodiments of the invention, the RH transmitter
120 measures the quantity of water vapor that exists in a gaseous
mixture of air and water that is exhausted from the system 100 in
the purge exhaust stream E. In this example embodiment, RH may be
defined as the ratio of the partial pressure of water vapor in the
gaseous mixture of air and water in stream P to the saturated vapor
pressure of water at a given temperature.
[0028] In example embodiments of the invention, the wet air inlet
stream W may be saturated with water vapor. With adequate membrane
surface area and a low ratio of purge to inlet flow, the saturation
level in the purge air will approach that of the inlet air prior to
reaching the purge exhaust port. In that embodiment, each unit
volume of purge air would carry the maximum possible volume of
water vapor such that the purge air is used efficiently. However,
the available membrane area would then be underutilized, because
once the purge air saturation level comes to equilibrium with that
of the wet air inlet stream W, the driving force for water vapor
diffusion goes to zero. To fully utilize the available membrane
surface, it is therefore desirable that the purge air saturation
level not approach that of the inlet air until the purge air
arrives at the purge exhaust port.
[0029] With the purge stream P set as described above, any
reduction in process flow causes the saturation level of the purge
exhaust stream E to fall, as there is less moisture available to
diffuse across the membrane 130 into a constant flow of purge air
P. The resultant reduction in the saturation level of the purge
exhaust stream E, as detected by the RH transmitter 120, indicates
an excess of the purge flow P. The RH signal 125 may be used to
modulate the purge flow control valve 110, which in turn minimizes
purge air consumption. For example, when the RH of exhaust stream E
decreases, the controller 115 may be configured to communicate to
the purge flow control valve 110 and enable it to decrease the
purge inlet air stream P.
[0030] Example embodiments of the invention may serve as an
energy-saving system due to the purge controller components, which
allow treatment of compressed air in a system that selectively
purges the membrane fiber bundle 130 as needed based on the
saturation level of the purge exhaust E. In example embodiments of
the invention, air is not lost through continuous or excessive
purging.
[0031] FIG. 2 is a schematic showing an energy management system,
according to another embodiment of the invention. In other
embodiments of the invention, a second RH transmitter 240 may be
installed at the dryer wet compressed air inlet I to detect the
inlet saturation level, as shown in FIG. 2. The controller 115
would receive analog output signals 117 and 247 from RH
transmitters 120 and 240, respectively. Accordingly, control may
then be established based on throttling the purge flow P as the
saturation level of the exhaust stream E falls below the saturation
level of the inlet stream W.
[0032] In example embodiments of the invention, a parallel series
of two or more on-off valves 250 may be used in the place of single
control valve 110, as shown in FIG. 2. The on-off valves 250, which
include for example, multiple solenoid valves, would then modulate
the purge flow P in discrete steps. In example embodiments, the
valves 250 may be offered in the same or in different sizes to
accommodate flow requirements. As such, the purge air inlet P may
be controlled by the on-off valves 250, which can electronically,
for example digitally, cycle the sweep on and off based on purge
air demand.
[0033] In example embodiments of the invention, the on-off valves
250 would each receive a separate valve control signal 125 from the
controller 115. The on-off valves 250 may be configured to
individually open and close to increase or decrease the purge inlet
flow P to match the purge requirements as the inlet contaminant
level, as measured by the RH transmitter 240, varies. The use of
solenoid valves rather than single continuously variable throttle
valves greatly decreases the cost of the system 200 while still
reducing purge consumption of the membrane fiber bundle 130.
[0034] FIG. 3 is a sectional view of a membrane dryer 307 having an
integral purge control feature used in conjunction with an energy
management system 300, according to another embodiment of the
invention. In example embodiments of the invention, the membrane
dryer 307 may have an integral purge control feature, as shown in
FIG. 3. Example embodiments include a purge control orifice 355 for
metering the appropriate amount of purge air and a purge flow
control valve 110 mounted to a purge manifold 357 located at the
bottom of the membrane dryer 307.
[0035] In example embodiments of system 300, the purge flow control
valve 110 may be a proportional solenoid valve or a continuously
variable flow valve or any other suitable valve that throttles
fluid flow. Concurrently, the rate at which purge exhaust exits the
purge outlet E may also be controlled by the diameter size of a
purge control orifice 355 which meters out sweep air. The diameter
size of the purge control orifice 355 can be varied depending on
the need of the user. Thus, the purge flow control valve 110
provides an electronic control of the sweep with a feed back
loop.
[0036] In example embodiments of system 300, the membrane dryer 307
operates similarly to the dryer 105 of systems 100 and 200.
Compressed air containing water vapor enters the dryer 307 through
the wet air inlet I. The compressed air passes through the membrane
fiber bundle 130. As the compressed air passes through the inside
of the membrane fibers, the water vapor is absorbed into the
membrane and passes quickly through the walls of the fibers to the
outer layers of the membrane fiber bundle 130. The bulk of the dry
air travels through a transfer tube 360 and leaves the dryer 307
through a dry air outlet D.
[0037] In example embodiments of system 300, a smaller portion of
the product dry air is diverted through a membrane bundle center
fitting 365, which also acts to center the membrane fiber bundle
130 within its housing 135. The purge air is then swept through the
sweep manifold 357 and into the purge flow control valve 110.
Similarly to systems 200 and 300, the RH of the purge exhaust
stream E is measured by RH Transmitter 120. The controller 115
would receive the signal 117 from the RH transmitter 120. The valve
110 is then continuously modulated by controller 115, which
receives its valve control signal 125 from the RH Transmitter 120.
For example, when the RH of exhaust stream E decreases, the
controller may be configured to communicate to the purge flow
control valve 110 and enable it to maintain modulated purge flow of
stream P. Accordingly, the system 300 maintains minimal purge flow
P through the membrane dryer 307.
[0038] In certain design conditions, when the wet air inlet stream
W is completely saturated, the purge exhaust may have an RH of
approximately 90%. If the rate of the wet air inlet flow W is
decreased by about 50%, for instance, then the rate at which water
vapor is conveyed into the dryer 105 will be reduced by
approximately 50% and the ratio of purge flow P to drying flow D
would ordinarily double. This increased P/D ratio causes the RH of
the purge exhaust stream E to fall and signifies excess purge. In
example embodiments of using the invention, when the RH transmitter
120 senses this reduction in RH of the exhaust stream E, the
controller 115 would signal the purge control valve 110 or valves
250 to reduce the flow until the purge exhaust rises once again to
about 90% RH. Accordingly, the purge flow P may be reduced by
approximately 50% to reach the about 90% saturation level of the
exhaust stream E, because about 50% less moisture is being
delivered to the membrane fiber bundle 130. This energy management
system 100, 200 or 300 would then result in a purge savings of 50%.
The same analysis could be applied to any given reduction in the
rate of inlet flow W.
[0039] Thus, the purge savings percentage is directly proportional
to the percentage reduction in inlet flow W. In other embodiments
of the invention, the controller 115 would be able to make similar
adjustments if there are changes in RH or pressure of the inlet
stream W which changes the rate at which water vapor is delivered
to the membrane fiber bundle 130 because the RH transmitter 120
would detect the resulting change in RH of the exhaust E. The
controller 115 would then receive the signal 117 from the RH
transmitter 120 and send a valve control signal 125 to the valve
110 to adjust the rate of the purge inlet flow P.
[0040] The many features and advantages of the invention are
apparent from the detailed specification, and thus, it is intended
by the appended claims to cover all such features and advantages of
the invention which fall within the true spirit and scope of the
invention. Further, since numerous modifications and variations
will readily occur to those skilled in the art, it is not desired
to limit the invention to the exact construction and operation
illustrated and described, and accordingly, all suitable
modifications and equivalents may be resorted to, falling within
the scope of the invention.
* * * * *